Work vehicles, especially construction vehicles, are often equipped with rollover protective fixtures and roll bars, which are fixed on the vehicle frame and extend upwards, to protect the operator in case of a overturning of the vehicle. If the work vehicle is equipped with a driver's cabin, the roll bar is normally integrated in the driver's cabin. However, if the work vehicle is furnished without a driver's cabin, the roll bar is normally built separately, whereby the roll bar is normally built as a U-shaped bar, whose free ends are fixed on the vehicle frame and whose cross members are essentially arranged above the head of the operator. Due to this, the roll bar is frequently that part of the vehicle that stretches farthest upwards.
Such an upward jutting roll bar can be disadvantageous, for example, during transport of the vehicle or during its operation.
To overcome this problem, roll bars equipped with folding mechanisms are known, which allow swinging away of the upper portion of the roll bar so as to reduce the height of the work vehicle. In general, these folding mechanisms have locks, with which the upper segment of the roll bar is arrested in a up-swung state against the lower stationary segment of the roll bar. Swiveling roll bars are known, in which the upper swiveling segment is connected with the lower, stationary segment by means of two bolts. Here one bolt works as a hinge, which is built stationary between both the segments. The other bolt can be removed and thus allows swiveling away of the upper segment. Here, the locking bolt is parallel to the swivel axis of the hinge.
The disadvantage thereby is that such a catch has some play due to the bolting and that the upper segment of the roll bar can swing out under operation related vibrations. Moreover, such a connection is difficult to manufacture.
To overcome this problem there are constructions, in which the upper segment of the roll bar is arrested through several screw connections, instead of through one bolt. The disadvantage thereby is that the removal of the screws to unswing the upper segment of the roll bar is possible only by using tools. Further, the screws are removed completely to swivel back the upper segment of the roll bar and can be lost easily. In addition to that, the screw connection must be made with the prespecified clamping torque and hence can be carried out only by trained personnel.
In the event of an overturn of the work vehicle, massive forces and moments arise, which work on the roll bars and must be absorbed by the vertical spars. Buckling, bending or breaks can occur in the area of the joint connection between the upper and the lower segments of the roll bar, since in general it is this part of the roll bar, which can least absorb the forces.